Although the prevalence of dental caries is continuing to decline, it so affects a majority of the U.S. population and can be a serious problem for those afflicted. Identification of such individuals prior to the onset of caries is of considerable importance, so that risk can be reduced or eliminated. The first long-term objective of this project is to develop and perfect a caries risk-assessment model which could be used to facilitate the targeting of caries-preventive activities on an individual or group basis (in both the private and public sectors), as well as in clinical research. Specific aims associated with this objective are 1) to develop, test, and refine a model for assessment of dental caries risk in children. This model involves combinations of previously identified measures from our preliminary studies related to dental caries, including salivary mutans streptococci (MS) and lactobacilli salivary calcium, phosphate, and fluoride, plaque accumulation, and history of prior exposure to fluoride; 2) to test the value of a dip-slide technique as an alternative to plating and counting salivary MS and lactobacilli; 3) to test other methods, eg. occlusal morphology and sociodemographic variables, for their potential usefulness as components of the risk-assessment model; 4) to facilitate development of a safe, non-invasive, accurate, and cost-effective battery of tests for caries risk assessment. The second long-term objective is to contribute to the understanding of the factors associated with the onset of enamel caries, so as to improve risk assessment. The specific aims associated with this objective are 1) to quantify salivary MS by biotype, 2) to preserve representative MS strains isolated from the study population, and 3) to initiate pilot studies at the molecular level to identify and characterize gene products that could affect caries susceptibility in humans. Based on the exceptionally encouraging findings from the investigators' prior cross-sectional and longitudinal studies, a comprehensive five-year longitudinal study involving 600 children will be conducted to farther develop and refine a caries-risk assessment model that will estimate the probability of a child developing clinically detectable dental caries within the succeeding six months. Clinical and historical data related to the specific aims will be gathered. Also, stimulated whole saliva will be collected for assessment of laboratory variables according to the specific aims. In addition to the development and refining of this model based on the first long-term objective, microbiological factors will be studied (see second longterm objective) for possible future inclusion in the caries risk assessment model. This proposed study will provide the first opportunity to investigate longitudinally the interactive roles of a number of selected pathogenic and protective risk factors in the assessment of caries risk.